1. Field of the Invention
The present invention relates to magnetic tape recorders and players and more particularly to an improved means of advancing a ratchet wheel in response to the reciprocating action of a solenoid piston and of aligning the elevation of the tape head with one of several tracks on a magnetic tape and of adjusting the azimuth alignment angle of the tape head.
2. Description of the Prior Art
Use of engaging arms in conjunction with the reciprocal motion of a solenoid piston for advancing a ratchet wheel is well known in the prior art. For example, U.S. Pat. No. 3,450,409--Pitzer discloses and discusses the theory of imparting rotary motion upon the ratchet wheel by reciprocal motion of a solenoid piston having ratchet engaging arms attached thereto. U.S. Pat. No. 3,632,114--Ban illustrates the use of two pivotally mounted engaging arms attached by a tee-bar to the piston of a solenoid for advancing a ratchet wheel as illustrated therein. U.S. Pat. No. 3,820,160--Huber discloses a frame-engaging arm arrangement connected to the end of a reciprocation piston.
The primary disadvantage of the prior art devices noted is that the engaging arms of these devices are either alternately in compression and tension or both in tension during engagement with the teeth of the ratchet wheel. The tensive action of engaging arms necessitates a "hook" at the end of each engaging arm which hook is subject to rapid wear and brings about unit failure after a relatively short life.
Also known in the art is the use of a cam mounted with a ratchet wheel on a shaft for coaxial rotation and a cam follower to effect changes in tape head support member elevation. For example, U.S. Pat. No. 3,820,180--Huber discloses an axial cam engaging a slidably mounted tape head support member. Such tape head support members are urged against the cam by a compression spring with a relatively high spring constant. The stability of the tape head support member, and consequently the tape head, in the direction of its sliding motion is dependent upon the compression spring strength. In some applications, such as automobile tape systems, the tape system is subjected to vibrations and impacts caused, for example, by bumps and other road irregularities. These vibrations and impacts cause the tape head to "bounce" against the compression spring and momentarily leave its position adjacent the recorded sound track, thus causing "voids" or "skips" in the sound emitted or recorded. If the compression spring strength is increased in an effort to minimize or eliminate "bounce," the cam follower is urged against the cam with greater force, impeding cam rotation and increasing the wear of the cam surface and the cam follower. There is no suitable means in the prior art to avoid "bounce" while at the same time minimizing the wear of the cam surface and the cam follower.
Adjustable tape head support members are also well known in the prior art as illustrated in U.S. Pat. No. 3,575,422--Peltz and U.S. Pat. No. 3,573,391--Harada. Peltz illustrates slidably mounted tape head support members constrained to move only in a vertical direction. As can be seen from Peltz, no provision is made for adjusting the azimuth angle of the tape head. In Harada, provision is made for adjusting the azimuth angle of the tape head, but the adjustment requires the balancing of at least two adjusting screws making accurate adjustment extremely difficult. U.S. Pat. No. 2,880,280--Gernert et al. discloses an adjustment system based on flexing a metal strip by a force exerted through rotation of a screw. Adjustment by the Gernert et al. apparatus, however, results in variation of the distance between the "head" and the "tape" and also, variation of the "head" elevation relative to the "tape." Thus, the prior art has failed to provide a satisfactory means of properly adjusting the azimuth angle so that the tape head sensors lie parallel to the magnetic tape without unwanted changes in tape head spacing and elevation.